Subba Rao, M. and R.D. Singh
ABSTRACT
In order to study the gene effects for various morpho-physiological characters related to drought tolerance in maize, generation mean analysis was performed in 3 different crosses and the results are summarized below.
Results indicated that mean values (m) were highly significant for all characters studied under rainfed as well as irrigated conditions. Under irrigated conditions, the interaction additive x additive was only found significant for days to 50% tasseling in cross Ib.62 x Ib.37. The type of epistasis was found to be complementary in one cross and it was duplicate in two other crosses studied. Under rainfed conditions, additive effect (d), dominance effect (h) and epistatic effects additive x additive (i) and dominance x dominance effect (l) were significant for the cross Ib.63 x Ib. 128. The type epistasis was found to be complementary in one cross while it was duplicate in nature in other two crosses studied. Dominance effect (h) and epistatic effect additive x additive (i) and dominance x dominance (l) were found significant for days to 50% silking under rainfed conditions. The type of epistasis was both duplicate and complimentary in different crosses studied. Dominance effect (h) was found to be significant in the cross Ib. 62 x Ib.128 while additive effect (d) was found significant for cross Ib.128 x Ib.145. Both additive effect (d) and additive x dominant effect (j) were found significant for cross Ib.62 x Ib. 37. The type of epistasis was duplicate in all the three crosses under rainfed and irrigated conditions. Dominance effect (h) and dominance x dominance interaction (j) were significant in cross Ib.62 x Ib.37 for the character plant height. Epistasis was duplicate in nature. For ear height under rainfed conditions, all the types of gene effects were found to be significant in different crosses studied. The epistasis was of duplicate nature.
Dominance effect (h) was found significant in cross Ib.128 x Ib.145 under irrigated condition for number of leaves per plant while under rainfed condition dominance effect (h) and additive x additive effect (i) were significant in cross Ib.62 x Ib.37. The type of epistasis was both complementary and duplicate. Additive effect (d) and dominance x dominance (l) were found for the cross Ib.62 x Ib.37. The type of epistasis was duplicate. For wilt ratings under irrigated conditions, all the gene effects (d,h,i,j and l) were highly significant in the cross Ib.128 x Ib. 145. Under rainfed condition the gene effects were non-significant for wilt ratings and canopy air temperature difference.
A perusal of the gene effects revealed that the estimates vary for each cross in different degrees. Significant occurrence of additive, dominance and epistatic components necessitates a breeding methodology like reciprocal recurrent selection or biparental mating or diallele selective mating which would be more useful to improve morpho-physiological characters related to drought tolerance.
Division of Genetics, Indian Agricultural Research Institute, New Delhi
Introduction
Maize is one of the most important cereal crops in India grown for grain as well as fodder
purpose. Nearly 65 per cent of maize is grown under rainfed condition. Moisture stress is a major limiting factor for maize production under
rainfed conditions. Global estimate indicates that there is a loss of about 15 per cent due to drought. Therefore, it is essential for enhancing the breeding effort for drought tolerance in maize. Drought is a complex phenomenon and depends on several characters like plants, maturity and physiological traits. Hence, it is essential to generate information on genetics of these traits. Keeping this in view, an experiment was conducted involving three crosses, respective inbred lines, F2 and two parental back crosses (BC1 and BC2). The results of these studies are described in this paper.
Material and Methods
The material for the study consisted of three crosses viz., Ib.62 x Ib.128, Ib.62 x Ib.37 and Ib.128 x Ib.145 along with respective parental lines and the two respective back crosses (BC1 and BC2) with male and female parents. The experimental material was grown in a randomized block design with 3 replications at Indian Agricultural Research Institute, New Delhi. The irrigated crop was grown with recommended number (5 irrigations during crop season) while rainfed crop was grown under purely rainfed conditions without any supplementary irrigation. Data were recorded on 5 plants for parents and hybrids and on 20 plants for F2 and back crosses. Observations were recorded on plant height, ear height, days to 50 per cent tasseling, days to 50 silking, anthesis silking interval (ASI),number of leaves/ plant, specific leaf weight, wilt ratings at seedling stage (1-5 scale) and canopy air temperature difference (CATD).
Recommended cultural practices were followed during crop growth. Genetic analysis was performed as per the six-parameter model described by Hayman (1958). Additive (d), dominance (h) and non-allelic effects i,j and l were calculated as per the generation mean analysis described by Hayman (1958).The estimates of h and l along with their sign were
utilized to understand the nature of epistasis. Results and Discussion
The results obtained from generation mean analysis for different characters studied are presented in table 1. Estimates of gene effects under irrigated and rainfed conditions are discussed below.
Maturity and plant characters
Results indicated that mean values (m) were highly significant for the characters studied for all the three crosses under rainfed as well as irrigated conditions (Table 1). Days to 50 % per cent tasseling
The interaction additive x additive (i) was found to be significant under irrigated condition in the cross Ib.62 x Ib.37. The type of epistasis was complimentary in this cross while this was duplicate in nature in other two crosses. Under rainfed condition, additive effect (d), dominance effect (h) and interaction dominance x dominance (l) were found significant in the cross Ib.62 x Ib.128. The type of epistasis was complimentary in Ib.62 x Ib.37 while it was duplicate in nature in other two crosses. Estimates of gene effects indicated predominance of non-additive gene effects for this trait. Additive gene effects were found important for days to 50 per cent tasseling by Gousenard et al. (1989) and Hemalatha and Sarkar (1990). Guo et al. (1986) reported predominance of dominance effects. Both additive and non additive effects were reported to be important by Ramesha (1988).
Days to 50 % silking
None of the gene effects were found significant under irrigated condition and type of epistasis was duplicate for all the crosses. Under rainfed condition, dominance effect (h) and epistatic effects additive x additive (i) and dominance x dominance effect (l) were found significant. The type of epistasis was duplicate
in Ib.62 x Ib. 128, Ib.62 x Ib.37 and complimentary in Ib.128 x Ib.145. Dominance effects were found important for this trait by Singh et al, (1979), while epistatic effects were found important by Saha (1981) and Ahuja et al. (1983).
Anthesis, silking interval
Dominance effect was found to be significant for the cross Ib.128 x Ib.145 under irrigated conditions. Under rainfed condition, dominance effect (h) and epistatic effect (i) were found significant in cross Ib.62 x Ib.128. In cross Ib.128 x Ib.145 cross, additive effect (d) was found significant while both additive effect (d) and additive x dominant effect (j) were found significant for cross Ib.62 x Ib.37. The type of epistasis was found to be duplicate in nature for all the three crosses under irrigated and rainfed conditions. Bonaparte (1977) found the importance of additive and dominance gene effects for this character, the magnitude of dominance effects being more important. Plant height
Under irrigated condition, none of the gene effects were found significant. Under rainfed condition, dominance effect (h) and dominance x dominance effect (l) were found significant in cross Ib.62 x Ib.128 while additive effect (d) and additive x dominance effect (j) were found significant in the cross Ib.62 x Ib.37. The type of epistasis was of duplicate nature. Singh et al (1975), Khalidi (1982) reported the importance of non-additive gene action for plant height while Hauller and Mirinda (1988) and Crossa et al (1990) reported the significance of additive gene action. Pal et al (1986), Debnath and Sarkar, (1987) reported that both additive and dominance gene effects were important. Marker and Joshi, (2005) indicated the importance of dominance variance for this trait though additive genetic variance was also found significant under rainfed condition.
Ear height
Under irrigated condition additive effect (d) was found significant in cross Ib.128 x Ib.145 while dominance x dominance epistatic effect (l) was found significant for cross Ib.62 x Ib.37. Under rainfed condition, dominance effect (d) and epistatic effects additive x additive (i)and dominance x dominance (l) effects were found significant for the cross Ib.128 x Ib.145 while only additive x dominance effect (j) were found significant in the cross Ib.62 x Ib.37. The type of epistasis was of duplicate nature in all the three crosses. The importance of both additive and non-additive gene effects were found important by Pal et al. (1986) and Debnath and Sarkar, (1987).
Physiological Traits
Mean effects (m) were highly significant for physiological characters for most of the crosses in both the moisture regimes. Estimates of gene effects for four physiological characters under two growing conditions are presented in table 2.
Number of leaves per plant
Dominance effect (h) was found significant in cross Ib.128 x Ib.145 under irrigated condition. The type of epistasis was of duplicate nature. Under rainfed condition, dominance effect (h) and additive x additive epistatic effect (i) were found significant in cross Ib.62 x Ib.37. The type of epistasis was duplicate in Ib.62 x Ib.37 and complementary in other two crosses. Sharma, (1987) and Brar and Labana (1991) reported the significance of additive gene effects for leaf number per plant.
Specific leaf weight
Dominance effect (h) and additive x additive epistatic effect (i) were found significant for cross Ib.62 x Ib.37under irrigated condition. The type of epistasis was duplicate in two crosses while it was complementary in 155
Ib.128 x Ib.145. Under rainfed condition, additive effect (d) and dominance x dominance effect (l) were found to be highly significant in cross Ib.62 x Ib.37. The type of epistasis was duplicate in the three crosses.
Wilt rating at seedling stage
All the gene effects (d,h,i,j and l) were found significant in cross Ib.12 x Ib.145. In the cross Ib.62 x Ib.128 dominance x dominance interaction (l) was found significant while additive effect (d) additive x additive effect (i) were found significant in cross Ib.62 x Ib.137. The type of epistasis was duplicate. Under rainfed condition, the gene effects were found to be non significant for this trait. Hemalatha and Sarkar (1990) reported greater importance of dominance variance for wilt ratings due to water stress.
Canopy air temperature difference (CATD) The gene effects were non significant for this character under rainfed and irrigated condition.
Estimation of various gene effects for different plant, maturity and physiological characters indicated the presence of additive, dominant and all the three digenic epistatic effects in various crosses studied. Hence, breeding procedures like reciprocal recurrent selection or biparental crosses or diallele selective mating would be useful tools to improve the characters related to drought tolerance. Blum (1979), Martinello (1983) and Ashok Kumar and Sharma (2005) earlier reported such breeding procedures .
REFERENCES
Ahuja, V.P., Mukharjee, B.K and Agarwal, K.N. 1983. Epistasis and its contribution to the expression of yield and other metric traits in maize (Zea mays L.). Genetika 15: 1-8 Ashok Kumar and Sharma, S.C.2005 Gene
action and heterosis for some quantitative
characters in bread wheat (Triticum
aestivum L). Indian J. Genet. 65: 281-
283
Blum, A. 1979. Principles and methodology of selecting for dourght resistance in sorghum.
Monografic de Genetica Agrano. 4: 205-
215
Bonaparte, E.N.A. 1977. Diallel analysis of leaf number and duration of mid silk in maize.
Can.J.Genet. Cytol. 19: 251-258.
Brar, G.P.S and Labana, K.S. 1991. Partitioning of quantitative variability for grain yield and its components in maize. In: Abstracts of Golden Jubilee Symposium on Genetic Research and Education: Currents trends and Next Fifty Years. Feb. 12-15,1991, New Delhi. 2: 385
Crossa, J, Vasal, S.K. and Beck, D.L. 1990. Combining ability estimates of CIMMYT’s tropical late yellow maize germplasm.
Maydica, 35: 273-278.
Debnath, S.C and Sarkar, K.R. 1987. Genetic analysis of grain yield and some of its attributes in maize (Zea mays L.). Thei. J.
Agric. Sci. 20: 263-276
Gouesnard, B, Gallas, A and Lefort-Buson, M. 1989. Intra and inter population genetic variability in two forage maize populations.
Agronomie 9: 867-876.
Guo, P.Z., Gardner, C.O and Obaidi, M. 1986. Genetic variation and gene effects controlling prolificacy and other traits in maize (Zea mays L.). Acta. Genet. Sin. 13 : 35-42.
Hallauer, A.R and Miranda, J.B.1988. Quantitative Genetics in Maize Breeding. Iowa State Univ. Press, Ames. P. 267- 294.
Hayman, B.I. 1958. The separation of epistasis from additive and dominance variation in
generation means. Heredity 12: 371-390. Hemalatha, G.V and Sarkar, K.R. 1990.
Genetical studies on some parameters of drought tolerance in maize. Phytobreedon. Khalidi, G.A. 1982. Genetic analysis of yield and
other quantitative characters in heterozygous populations of maize (Zea mays L.) M.Sc. Thesis. IARI., New Delhi.
Martinello, P. 1983. Outlines of major components of maize breeding progrmmes for semi-arid regions (Capitanata plain). Genet. Agr. 37: 361-390.
Marker, S and Joshi, V.N. 2005. Genetic analysis of maize (Zea mays L.) composite under stress and non-stress conditions. Indian J. Genet. 65: 211-212
Pal, S.S, Khera, A.S and Dhillon, B.S. 1986. Genetic analysis of and selection advance in maize populations. Maydica. 31: 153- 162.
Ramesha, M.S. 1988. Genetic study of some rare quantitative characters in maize (Zea mays L.), M.Sc . Thesis; UAS., Dharwad.
Saha, B.C. 1981. Nature of inheritance and heterosis manifestation in physiological and agronomic attributes in hybrids of maize (Zea mays L.). Ph.D. thesis, IARI, New Delhi.
Sharma, J.K. 1987. Study of Genetics of some morphological, physiological and biochemical characters associated with drought resistance in maize (Zea mays L.). Thesis abstracts. H.P. Krishi Viswavidyalaya, Palampur, P.107-108. Singh, R.D, Joshi, A.B, Dhawan, N.L and
Mukharjee, B.K. 1975. Studies on elite Indian maize composites. I. Genetic analysis of grain yield and other agronomic traits. Genetika. 7 : 26-268.
Singh, A.K, Dixit, R.K and Singh, H.G. 1979. Combining ability analysis for yield and its attributes in maize (Zea mays L.). Indian J. Agric. Res. 13: 27-30.
Spangole, W.E. 1986. Moisture stress response in maize. Diss. Abst. Internat. B46: 2135B
Table 1. Estimates of gene effects for maturity and plant characters in maize under irrigated
and rainfed conditions.
*, ** : Significant at 5% and 1% level, respectively
1. Ib 54.33** -1.67 -2.33 4.67 0.33 -2.00 Complementary 2. Ib 55.33** 2.67 5.33 8.00* 2.00 -14.67 Duplicate 3. Ib 58.67** -2.33 -4.00 -3.33 -2.67 16.00 Duplicate 1. Ib 65.00** -2.67* -19.83* -18.67* 0.5 32.99** Duplicate 2. Ib 64.67** 3.33 -5.00 -2.67 4.67 -7.33 Complementary 3. Ib 65.33** -0.33 12.00 11.33 -0.33 -12.00 Duplicate 1. Ib 61.67** -2.33 -8.83 -6.67 -1.67 0.33 Duplicate 2. Ib 61.33** 0.33 2.67 3.33 1.00 -5.33 Duplicate 3. Ib 65.00** -4.00 -11.33 -8.00 -3.00 24.00 Duplicate 1. Ib 72.67** -1.67 -28.97** -25.99** 2.67 44.67** Duplicate 2. Ib 72.00** -0.67 -10.17 -10.17 -0.17 8.33 Duplicate 3. Ib 74.67** 3.00 2.83 2.00 1.83 1.00 Complementary 1. Ib 7.33** -0.67 -6.5 -5.33 -0.50 2.33 Duplicate 2. Ib 6.00** -2.33 -2.67 -4.67 -3.00 9.33 Duplicate 3. Ib 6.33** -1.67 -7.33* -4.67 -0.33 8.00 Duplicate 1. Ib 7.67** 1.00 -9.17** -7.33* 2.17 11.67 Duplicate 2. Ib 7.33** -4.00* -5.17 -8.00 -4.83* 15.67 Duplicate 3. Ib 9.33** 3.33* -9.17 -9.33 2.17 13.00 Duplicate 1. Ib 149.33** 3.33 78.67 44.00 -12.00 -89.33 Duplicate 2. Ib 160.33** -0.67 11.83 -19.99 -7.17 24.33 Complementary 3. Ib 138.67 13.67 25.33 15.33 17.99 -82.67 Duplicate 1. Ib 127.00** 5.33 137.50* 120.00 -7.50 -189.67* Duplicate 2. Ib 137.33** -36.00* 60.83 29.33 -47.83** -17.67 Duplicate 3. Ib 107.33** 3.33 67.99 59.99 -6.99 -102.67 Duplicate 1. Ib 56.67** 2.67 24.99 9.33 -4.00 -40.67 Duplicate 2. Ib 56.00** -10.00 7.67 -20.00 -10.00 71.33* Complementary 3. Ib 45.33** 13.00* 14.00 8.67 12.33 -44.00 Duplicate 1. Ib 50.67** 10.33 48.33 40.67 3.33 -63.00 Duplicate 2. Ib 49.67** -16.00 38.83 24.00 -20.50* -4.33 Duplicate 3. Ib 40.00** 7.33 26.67* 21.33* 0.67 -40.00* Duplicate 1.Days to 50% Tasseling 2. Days to 50 % silking 3. Anthesis silking Interval 4. Plant height (cm) 5. Ear height (cm) a) Irrigated b) Rainfed a) Irrigated b) Rainfed a) Irrigated b) Rainfed a) Irrigated b) Rainfed a) Irrigated b) Rainfed
Character EnvironmentCross Gene Effects Type of
epistasis
Table 2. Estimates of gene effects for physiological characters in maize under irrigated and
rainfed conditions.
*, ** : Significant at 5% and 1% level, respectively
1. Ib 62x 13.07** 0.80 -2.73 -3.47 -1.00 2.93 Duplicate Ib 128 2. Ib 62 x 12.20** -0.23 -0.83 -1.00 -3.99 3.27 Duplicate Ib 37 3. Ib 128 x 10.33** 1.20 5.33* 3.73 1.07 -2.93 Duplicate Ib 145 1. Ib 62 x 11.27** 0.33 2.45 0.93 -0.58 0.69 Complementary Ib 128 2. Ib 62 x 11.53** -0.27 4.78** 3.47* -1.05 -5.30 Duplicate Ib 37 3. Ib 128 x 10.87 0.37 -1.75 -1.53 0.05 -1.17 Complementary Ib 145 1. Ib 62 x 6.39** 0.50 -2.00 -2.83 0.43 5.02 Duplicate Ib 128 2. Ib 62 x 6.61** 0.51 -3.50* -3.46* 0.68 4.66 Duplicate Ib 37 3. Ib 128 x 5.84** 0.35 -0.74 -0.44 0.21 -0.67 Complementary Ib 145 1. Ib 62 x 7.26** 1.83** 2.85 1.72 1.31 -6.49* Duplicate Ib 128 2. Ib 62 x 6.49** 2.08** 3.63 3.46 2.51** -5.00 Duplicate Ib 37 3. Ib 128 x 7.00** 0.10 0.42 -1.47 -0.26 -1.12 Duplicate Ib 145 1. Ib 62 x 1.33** 0.00 -2.00 -1.33 0.33 4.00** Duplicate Ib 128 2. Ib 62 x 1.00** 0.67* 0.67 1.33** 0.67 1.33 Duplicate Ib 37 3. Ib 128 x 2.00** -1.00** -2.17** -2.00** -0.83** 5.67** Duplicate Ib 145 1. Ib 62 x 2.67** -1.00 -0.33 -0.67 1.00 3.33 Duplicate Ib 128 2. Ib 62 x 3.33** 0.67 -0.50 0.00 0.83 -1.67 Complementary Ib 37 3. Ib 128 x 3.00** -0.33 3.83 3.33 -0.17 -5.00 Duplicate Ib 145 1. Ib 62 x -2.06* -0.97 -1.12 -3.27 -0.55 8.37 Duplicate Ib 128 2. Ib 62 x -1.60 -0.23 -10.85 -10.20 0.22 13.17 Duplicate Ib 37 3. Ib 128 x -2.53** 0.27 -2.30 -2.40 -0.37 3.53 Duplicate Ib 145 1. Ib 62 x -0.33 0.17 -8.00 -6.87 2.53 11.87 Duplicate Ib 128 2. Ib 62 x -1.70 2.00 -5.37 -6.00 2.03 13.80 Duplicate Ib 37 3. Ib 128 x -1.06 -0.23 1.73 2.47 -0.20 2.53 Complementary Ib 145 1. No. of leaves per plant 2. Specific leaf weight (g) 3. Wilt rating at seedling stage 4.Canopy air temperature difference ( 0 C) a) Irrigated b) Rainfed a) Irrigated b) Rainfed a) Irrigated b) Rainfed a) Irrigated b) Rainfed
Character Environment Cross Gene Effects Type of
epistasis
m d h I j l